GM: Electra/Park Avenue/Ninety-Eight 1990-1993

Valves and Springs

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Fig. Fig. 1 View of valve and related parts



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Fig. Fig. 2 Checking valve spring height



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Fig. Fig. 3 Checking valve spring load



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Fig. Fig. 4 Measuring valve spring installed height



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Fig. Fig. 5 Reaming the valve guide



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Fig. Fig. 6 Valve wear patterns



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Fig. Fig. 7 Measuring valve guide clearance

REMOVAL & INSTALLATION



  1. Remove the cylinder head(s) from the vehicle as previously outlined.
  2.  
  3. Using a suitable valve spring compressor, compress the valve spring and remove the valve keys using a magnetic retrieval tool.
  4.  
  5. Slowly release the compressor and remove the valve spring caps (or rotators) and the valve springs.
  6.  
  7. Fabricate a valve arrangement board to use when you remove the valves, which will indicate the port in which each valve was originally installed and which cylinder head. Also note that the valve keys, rotators, caps, etc. Should be arranged in a manner which will allow you to reinstall them on the valve on which they were originally used.
  8.  
  9. Remove and discard the valve seals. On models using the umbrella type seals, note the location of the large and small seals for assembly purposes.
  10.  
  11. Thoroughly clean the valves on the wire wheel of a bench grinder, then clean the cylinder head mating surface with a) a soft wire wheel, b) a soft wire brush, or c) a wooden scraper. Avoid using a metallic scraper, since this can cause damage to the cylinder head mating surface, especially on models with aluminum heads.
  12.  
  13. Using a valve guide cleaner chucked into a drill, clean all of the valve guides.
  14.  
  15. Reinstall each valve into its respective port (guide) of the cylinder head.
  16.  
  17. Mount a dial indicator so that the stem is at 90° to the valve stem, as close to the valve guide as possible.
  18.  
  19. Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator.
  20.  
  21. Measure the valve stems using a micrometer, and compare to specifications, to determine whether stem or guide wear is responsible for excessive clearance. Consult the Specifications tables earlier in this Section.
  22.  

VALVE SPRING TESTING



Place the spring on a flat surface next to a square. Measure the height of the spring and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1 / 16 inch (1.6mm) or if distortion exceeds 1 / 16 inch (1.6mm), replace the spring. In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Spring pressure should be - 1 lb. (0.45kg) of all other springs in either position.

REFACING



Using a valve grinder, resurface the valves according to specifications in this Section. All machine work should be performed by a competent, professional machine shop.

Valve face angle is not always identical to valve seat angle.

A minimum margin of 1 / 32 inch (0.8mm) should remain after grinding the valve. The valve stem top should also be squared and resurfaced, by placing the stem in the V-block of the grinder, and turning it while pressing lightly against the grinding wheel. Be sure to chamfer the edge of the tip so that the squared edges don't dig into the rocker arm.

LAPPING



This procedure should be performed after the valves and seats have been machined, to ensure that each valve mates to each seat precisely.

  1. Invert the cylinder head, lightly lubricate the valve stems, and install the valves in the head as numbered.
  2.  
  3. Coat valve seats with fine grinding compound, and attach the lapping tool suction cup to a valve head.
  4.  

Moisten the suction cup.

  1. Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving.
  2.  
  3. Lap the valve until a smooth, polished seat is evident.
  4.  
  5. Remove the valve and tool, and rinse away all traces of grinding compound.
  6.  

 
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